A repurposing of older term 辞書(jisho, “letter of resignation”, see below), based on a reanalysis of the constituent characters 辞(ji, “resignation, quitting; word”) + 書(sho, “writing, record, document, book”). Influenced by Middle Chinese-derived term 辞典(jiten, “dictionary”), wherein the 辞 character expresses the meaning word from Middle Chinese辭(zi), instead of the meaning resignation or quitting from Middle Chinese辤(zi). Note that both of these older character forms were later conflated in both Japanese and Chinese into the simplified version 辞, with the word meaning becoming dominant in Chinese.

First appearance in Japanese with the dictionary sense might be the 1595 publication by the Jesuits of the 羅葡日辞書 (Ra-Ho-Nichi Jisho, “Latin-Portuguese-Japanese Dictionary”), alternate title Dictionarium Latino Lusitanicum, ac Iaponicum.[1]

Compare modern Mandarin辭書(císhū, “dictionary, lexicon”), possibly reborrowed from or otherwise influenced by the Japanese.